During the winter months, it's a great time to appreciate evergreen shrubs and trees.
Pine trees are particularly impressive due to their large stature. Generally, pines tend to tolerate poor soil conditions and environmental stress better than fir and spruce. Although many species are available, five pines are recommended in Missouri.
Eastern white pine (Pinus strobus) is easily recognized by its bluish-green, soft, flexible foliage with five needles per fascicle (bundle). These trees are fast-growing and are often over 50 feet tall at maturity. However, trees can also be sheared and maintained as a hedge. White pine begins bearing cylindrical cones (4-8 inches long) at a relatively young age. It is best suited to full sun and moist, well-drained soils, but can tolerate some stress. Limb breakage can occur during periods of high winds or heavy wet snow. White pine blister rust, which is a common disease in other states, is not problematic in Missouri.
"Vanderwolf's Pyramid" limber pine has long silvery blue-green needles with flexible and slightly twisted branches.
Limber pine (Pinus flexilis) is another pine with flexible branches and five needles per fascicle. However, this species is slower growing than Eastern white pine and ranges from 30-50 feet tall at maturity. The cultivar, "Vanderwolf's Pyramid," has a dense tree form and is often available at nurseries. Cones are light brown in color and range from 3-6 inches long. Limber pine is considered a low maintenance tree and serious pests are uncommon on these trees in Missouri.
In contrast to the former pines, Austrian pine (Pinus nigra) has dark green, rigid needles with sharp tips and are borne in fascicles of two. Cones are produced singly or in clusters and are 2-3 inches long. Austrian pine will tolerate a wide range of soil types if provided adequate moisture. Trees will grow to over 50 feet tall at maturity.
Although these pines are nice specimens, they are susceptible to Diplodia tip blight disease, which causes needle browning and branch dieback. Infection occurs during wet periods in spring and early fall. Needles begin to die several weeks after infection. Symptoms of this disease often begins on the lower portion of the tree and progress upward. Trees weaken by drought, hail, snow, compacted soils, insect activity, or mechanical wounding are particularly susceptible to Diplodia tip blight disease.
Pitch loblolly or pitlolly pine (Pinus rigida x taeda) is a hybrid that reaches 60 feet at maturity. These trees are fast growing, with good winter hardiness, drought and heat resistance, and tolerance to poor soils. These trees have three needles per fascicle, and cones are about 3-4 inches long. Pests are generally not problematic unless trees are subjected to stress.
Japanese black pine (Pinus thunbergii) trees generally grow to 20-60 feet tall. Because it has an irregular growth habit, this species is most often used in informal landscapes. Its dark green, stiff needles are borne in fascicles of two. Japanese black pine can be grown in a wide range of soils and tolerates hot, dry weather. However, needle and terminal shoots can be injured by a rapid temperature drop in late fall or winter. Healthy trees are generally unaffected by pests.
Although Scotch pine (Pinus sylvestris) is commonly sold, these trees are not recommended for planting in Missouri. Scotch pine does not tolerate wet or dry soils. Scotch pine is also susceptible to pine wilt, which results in tree mortality, as well as other pine needle blights and pine needle scale (Chionapis pinifoliae).
Although pine needle scale is most common on Scotch pines, it will also infest other pines. These white-colored scales infest the surface of needles, which turn brown and die. Heavy infestations can cause branch or tree mortality. Light infestations can be controlled by pruning and/or the application of insecticidal soap (Neem). Alternatively, an application of dormant oil in late March or early April before new growth is initiated is effective.
Larvae of the Eastern pine shoot borer (Eucosma gloriola) can infest the two and five needle pines, but it doesn't usually cause tree death. Feeding begins in the spring and is generally completed by late June. When pines are infested with this insect, shoot tips flag. When shoot tips are inspected, their oval exit holes are visible. Prune and destroy infested shoots when flagging is observed. Larvae of the European pine shoot moth (Rhyacionia buoliana) also tunnel through tissue while feeding, initially entering at the base of needles or buds of pines before moving into in the shoot tips. Infested shoots have discolored needles and buds are often coated with resin. Later in the growing season, dead or deformed shoot tips are visible. Infested shoots can be pruned while larvae are present or an insecticide, such as carbaryl (Sevin), may be applied.